As per https://docs.aws.amazon.com/cur/latest/userguide/pricing-columns.html both pricing/publicOnDemandCost and pricing/publicOnDermandRate will not reflect tiered pricing across any services currently.
Instead the highest available rate will be used e.g for CloudFront DataTransfer the "First 10TB" values would be utilized - https://aws.amazon.com/cloudfront/pricing/